At present, it is commonly acceptable to utilize various cheap organic row materials present in the wastes of agricultural or industrial manufactures for the production of animal feed products. Therefore, available agricultural and industrial wastes represent a valuable resource for microbiological synthesis of such feed; their fermentation is of considrable practical importance. One should also bear in mind that manufacturing food products per se from organic wastes is only one aspect of their utilization while another and not less important one is the environmental aspect, since the utilization of wastes is associated with cleaning of the environment therefrom.
There is a known-in-the-art method for producing proteinaceous animal fodder from organic vegetable wastes by bio-degradation thereof with subsequent fermentation.
In U.S. Pat. No. 5,198,252, Simsa et al. discloses a method for the manufacture of fodder and/or soil improving agents by anaerobic or aerobic fermentation of vegetable environmental wastes such as aquatic plants, specifically the water hyacinth (Eichhornia crassipes).
The known method comprises the comminuting of harvested plants, mixing them with the organic waste material of the food industry and/or agriculture industry, adding to the mixture an inoculating agent, a biological degradation agent and a starter culture and, finally, anaerobically fermenting the mixture for 2-45 days.
An inoculating agent is selected from the group including a pectin cleaving enzyme and a thermophillic lactic acid bacterial culture. A degradation agent is chosen from the group consisting of molasses, urea and organic carboxylic acids, and a starter culture having high cellulase activity is selected from the group consisting of Trichoderma viridae, Chaetonium globusum and Actinomycetes.
There are a number of serious disadvantages associated with the method disclosed in the above patent. The first of these disadvantages lies in the fact that the known method requires mixing of the comminuted wastes with a ready-to-use commercially available enzyme, namely pectinaze, which is a relatively expensive product and has reduced cleaving efficiency compared with the efficiency of an enzyme which could be formed in situ by a microorganism during the bio-conversion process itself.
Another significant shortcoming of the known method is the introduction of molasses, which is a source of glucose and pentozes. It is well known that these carbohydrates inhibit the hydrolysis process effected by a starter culture and thus reduce the efficiency of the whole bio-conversion process. As a result the cellulose initially contained in aquatic plants and vegetable wastes may remain unconverted within the fodder. Furthermore, the above carbohydrates inhibit the fermentation of the starter culture pectinaze, thus preventing the hydrolysis of pectine initially contained in wastes. Pectin may also remain unconverted in the fodder. All of the above are associated with receiving a food product which has a high content of cellulose and low digestibility.
Unfortunately, the introduction of molasses is associated with even more disadvantages, namely, with the fact that the formation of organic acids during biological degradation and fermentation of the mixture takes place because of the hydrolysis of cellulosic products contained in the waste itself, i.e. cellulose, hemicellulose, lignin, and not because of the fermentation and assimilation of carbohydrates contained in molasses. This also reduces the efficiency of the bio-conversion process and thus the quality of the final product.